Method of and apparatus for cutting plaster board or analogous materials



A June 11, 1929.

.1. J. TURNER METHOD OF AND APPARATUS FOR CUTTING PLASTER BOARD OR ANALOGOUS MATERIALS Filed May 28, 1923 Patented June 11 1929.

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OPE-PORTION 01' DELLWA'BI.

BILLS.

Application filed lay 28,

Thisinvention relates to methods for cutting plaster board or analogous materials and to a knife for use in connection with the method of cutting. In the manufacture of plaster board, plas ter in semiliquid or lastic condition is fed.

between two sheets 0 paper'or other fibrous material and is passed through machinery for forming theboard, the board being in a 1 substantially endless strip or sheet. After the board has been completely formed and while the core is still only partially dried and hardened, the board is cut into lengths that can be easily handled and the drying and the hardening of the plaster core are com leted after the cutting operation. While the card is in this soft or plastic condition, great care must be taken that thepaper is not torn from the core byv the knife, since otherwise the edge portion of the board will be defective and not usable to the best advantage in building construction. Owing to the softness of the core, the difliculty presents itself that if a guillotine cutter comprising a knife of ordinary construction is used, the core will be squeezed by the knife due to the fact that the paper covering is tough and very much harder to cut than the soft core, so that the edges of the board will not be of uniform thickness.

The objects of this invention are to provide a method of cutting plaster board in such a manner that the paper will not be loosened from the core, and so that the soft core will not be squeezed out 'or otherwise damaged by the pressure exerted thereon by the cutting knives; also to provide a cutting knife of hue proved construction for use in severing plaster board while the corethereof is in soft or plastic condition; also to' improve methods of this kind, and knives for cutting plaster board in the other respect hereinafter specified. 1

In the accompanying drawings:

Fig. 1 is a fragmentary transverse section of a strip of plaster board passing through the forming machinery and showing the same in operative relation to the knives embodying this invention, parts only of the knives being shown in elevation. v I

. Fi s. 2 and 3 are similar fragmentary views showlng the knives in different positions with 1m. Serial Io. 041,027.

means for giving the knives their operativeapparatus for cutting the same, showing my improved method for cutting plaster board. Fig. 8 is an inside face view of the cam at one end of the bottom knife bywhich the knife is moved vertically in unison with its horizontal movement; and Fig. 9 is a. face view of thecam by which the knives are moved horizontally. I

For the purpose of producing a strong, light weight plaster board having a plaster core made without-sawdust or other similar material, it has recently been found possible to mix plaster of Paris with a greater amount of water than has heretofore been used in plaster board cores, which water is removed during the drying of the board. Conseemulatin quently, the board, while passing through the the edges thereof, but I do not intend to limit the invention to such use, since the invention can be used to good advantage in cutting other kinds of plaster board or analogous materials.

A represents the board which is to be cut and which includesthe usual core a of plastic material, the opposite faces of which are covered by meansof sheets of paper a. or other fibrous material.

The cutting of the board is preferably effected by means of a pair of knives B and C which are normally positioned beyond opposite faces of the board and between which the board passes on its way to the discharge end of the board-forming machine. The knives shown are moved in the direction indicated by the arrows, directly toward each other, there being no movement of the knives in the direction of their length. The cutting edges of the knives are provided with a plurality of substantially V-shaped teeth 6 and c, and the edgeportions of these. teeth are sharpened so as to effect the cutting. The two knives are preferably so arran ed t at the teeth of one knife will enter mto the spaces between or mesh wit-h the teeth of the other knife, and consequently during the movement of the knives toward each other, the sharp points of the V-shaped teeth will first pierce the paper or fibrous covering material of the board. Then upon further penetration into the board. the opposite sharpened edges of each tooth will extend the cuts into the covering material in opposite directions and at the same time the teeth will penetrate into the core of the board. Consequently, during the cutting stroke of the knives, first penetration of the sharpened points of the teeth through the paper or covering material will cause very little pressure to be exerted against the flat faces of the board, and durin the further penetration of the teeth, considerable of the force required to cut the paper is exerted substantially in a direction parallel to the flat faces of the board, so that very little force is exerted in a direction to squeeze the soft core of the board. Consequently the knives make a clean cut in the board and leave the cut edges of the board undamaged. It has been found that the best results are obtained by having the teeth penetrate only partially through the board so that the two knives do not meet at the completion of their cutting strokes, as shown in Fig. 3, with the cutter at each face severing the paper at the corresponding face only without penetrating the paper at the opposite face.

Since the cutting of the boardis effected while the board is moving continuously through the machine, my rocess includes the moving of the knives wit the board 'during the cutting operation, so that during the movement of the knives toward each other to penetrate the board, the two knives move with the board and at the same rate of travel as the board, so that there is no relative movement between the knives and the board in the direction of the length of the board, as shown in Figs. 4 and 5, This movement of the knives with the board continues until the knives have completed the cutting stroke, Fig. 5, whereupon the knives are given a short movement in the same direction as the movement of the board but at a greater rate of speed. This 7 short movement of the knives pushes the strip of board which has been cut off in advance of the remaining portion of the board, as shown in Fi 6, and

serves the two-fold purpose, in the rst place of completing the separation of the two parts of the board at the point ofthe cut by a tearing or separatin action, and furthermore forms an enlarge space between the two sections of the board through which the knives a may pass in their return stroke, as shown in Fig. 7, without contactin' with either of the I vertically between two spaced slide bars 11- which in turn are supported by slide blocks 12 which are slidable horizontally between two spaced slide bars 13 rigidly mounted 1n.

position. The slide blocks 12 are moved hori-' zontally for giving the knives a corresponding movement by means of links 14 pivotally connected therewith, the forward end of the link 14 at each side of the machine being provided with a roller 15 which works in a cam 16 mounted upon a shaft 17 revolublymounted in transverse position with respect to the machine. The cam groove in each of the cams is so shaped that when the cam is rotated in counter-clockwise direction in Fig. 9 the link is drawn at a uniform speed of movement toward the right in said figure corresponding to the speed of movement of the board A until the roller 15 is brought into enfor givin the knives gagement with the portion of the cam groove indicated at 18, at which time the speed of movement of the link is quite materially increased so as to cause the knives to move con-' I have provided rollers 20 which engage in.

cams 21 rigidly mounted in position at opposite sides of the machine. These cam grooves are so shaped that, as the knives are moved forwardly with the board by the links 14 actuated by the cams 16, the upper knife is moved downwardly and the bottom knife is moved upwardly for operation as above 'de-. scribed. A spring. 22 is provided at the lower portion of the cam groove of the lower cam 21 for throwing the roller20 past the critical point with respect to the return movement of the link 14 for causing the roller to continue about the groove in lieu of retracing its path. The upper cam 21 is, of course, just the reverse of the lower cam.

This method and the knives of the construction described have made possible the.

out much more easily and with less wear on the knives than is the case with other knives or cutters heretofore used, and with less wear on the mechanism for actuating the knives. This is probably due to the fact that the knives enter the board gradually, since at first only the points of the knives enter the surface of the board, and then due to the inclination of the cutting edges, a further gradual cutting of the fibrous covering of the board results. The knives consequently make a drawing cut, rather than'a shearin cut, which results in a saving of power an also enables the cutting edges of the knives to remain sharp for much longer periods of time than is possible with straight edgedcutters.

I claim as my invention:

1. The hereindescribed method of cutting material having a relatively soft core and relatively tough covering layers while the same is moved in the direction of its length, consisting of forcing knives in o posite directions against opposite faces 0 the board to cut through the greater portion of the board, the knives and board travelling approximately at the same rate of speed during the penetration of the knives into the board, and completing the severin of the board by moving the knives in the direction of movement of the board and at a greater speed than the movement of the board, to form an opening at the line of cut throu h .which the knives move away from each 0t er out of engagement with the twoparts of the board.

2. The method of cuttin sheet material having a soft core interpose' between layers of relatively tough material, which consists in simultaneously puncturing each layer at spaced points along the line of the proposed cut, and then cutting entirely through the layer ateach face ofthe sheet material between said punctures by forcin therethrou h the divergent cutting edges of the teeth of a cutter at that face.

,3. The method of cutting sheet material having a soft core interposed between layers of relatively tough material, which consists in inserting the opposed edges of a air of cutters into the oppositesides of the s eet of material so as to cut through the two layers of tough the soft core, then giving the cutters ,amoveaterial and substantially divide ment horizontally for moving one severed portion of the sheet material edgewise away rom the other portion. and then moving the cutters edgewise away from each other for clearing the sheet of material.

4. The hereindescribed method of cutting material having a relatively soft core and relatively tough covering layers, com rising moving the material longitudinally, orcing knives, having a plurality of V-shaped cutting edges terminating in points, against the opposite faces of the board, causing said points to penetrate said covering layers, then forcing said knives to penetrate farther into said boards to exert cutting strains substantially parallel to the fiat faces of the board, moving said knives during their cutting action in the direction of movement of the board, and moving said knives after their cutting stroke is completed in the direction of movement of said board at a higher rate of speed than the speed of said board, to separate the cut edges of the board.

5. The method of cutting a moving sheet of material which comprises passing the sheet of material between opposed cutters, then moving the cutters with the sheet of material and simultaneousl inserting said cutters into the opposite 'si esof the moving sheet of material so as to divide same, then moving the severed portion away from the remainder of the sheet of material and moving the cutter edgewise of the sheet" out of contact therewith, and then moving the cutters edgewise away from each other for clearing the sheet of material.

6. A cutting device of'flasterboard and the like, including a pair 0 knives movable toward each other at opposite faces of the board, each of said knives being provided with pointed teeth adapted to perforate the faces ofthe board and then to enlarge the perforations by the action of the obliquel disposed cuttin edges of the pointed teeth until the sever perforations are completely united at the bases of the teeth the points of the teeth enterin either of the faces of the board being sti in substantial spaced relation with respect to the other face of the board after the complete severance of the face portions.

JOHN J. TURNER. 

